170 RED EOT OF SUGARCANE. 



of the midrib were reached ; these were then penetrated (Fig. 1). 

 As is already known, the germ-tubes of the spores readily form 

 appressoria (described mider the name of " gemmae " by Went 

 and of chlamydospores by most other writers). These are thick- 

 walled, durable cells, capable of surviving detachment from the 

 mycelium. It is probable that they serve a double purpose 

 of close adhesion to the surface of the host plant and of accumu- 

 lation of enzymic energy to secure penetration of its walls. In 

 Colletotrichum falcaium the infection hypha seems to arise as 

 a rule from an appressorium (Figs. 1 and 2). Entry through 

 stomata was not observed, the infection hypha passing directly 

 across the outer wall of an epidermal cell, or, in some cases, 

 down between the side walls of two cells. After entry, the 

 hypha) may at once branch freely and fill the large motor cells 

 with a mass of mycelium, or may penetrate deeply into the leaf, 

 passing from cell to cell with ease in the large-celled parenchyma 

 between the bundles, but not readily entering the latter. In 

 some cases the sclerenchyma was penetrated, but usually, when 

 the loaf had not been injured before inoculation, the hyphse 

 remained, for the first week at least, confined to the thin- walled 

 cells. In the cases where the leaf was first wounded, conditions 

 were somewhat different. There was a superficial growth as 

 before, extending beyond the limits of the wound. But penetra- 

 tion was not now confined to the thin- walled motor cells but 

 occurred freely into the epidermis of the midrib just beyond 

 the wounded part (Fig. 2), and the mycelium ramified through 

 the sclerenchyma as readily as through the parenchyma. In some 

 cases, the layers of underlying sclerenchyma left after removing 

 the epidermis, were an effective barrier and penetration only 

 occurred beyond the midrib into the thinner tissues between the 

 bundles, but in others, presumably when the injury was more 

 severe, the thick-walled tissues showed much myceliun). All (he 

 invaded tissues developed a bright red colour. 



In less than a week fructification may occur on the mfected 

 spot. The hyphse first collect in masses in the epidermis, through 



